The aim of this research is to analyze central nervous system regeneration in the snail Melampus bidentatus. The snail's simple nervous system and the presence of identifiable neurons will allow a detailed study of functional pathways that are reestablished following injury to the nervous system. Regeneration following the removal of the cerebral commissure, transection of the cerebropedal and cerebropleural connectives and ablation of one cerebral ganglion will be investigated. The approach to analyzing regeneration will be to compare the neuronal circuitry known to underlie behaviors in normal animals with that formed during regeneration. The following techniques will be used: 1) Behavioral. Cerebral commissure ablation interferes with bilateral tentacle retraction responses to unilateral stimuli; connective transection interferes both with tentacle retraction and whole body withdrawal and also causes the snail to crawl in circles. Preliminary results indicate that restoration of normal behavior in each case is dependent upon regeneration. 2) Anatomical. Regeneration will be studied with the aid of cobalt chloride backfilling and dye iontophoresis, histological detection of changes accompanying neuron regeneration, and electron microscopical examination of regenerating processes and neuropile. 3) Electrophysiological. Detailed information about the normal neuronal circuitry underlying the behaviors described in 1) will be determined using intracellular and extracellular recording and stimulating techniques. The synaptic connections that are interrupted by the operations on the nervous system will be compared for normal and regenerated animals.